Old Dominion Electrical Cooperative Wildcat Intake

Trenchless Technology

old dominion aerial view hole

Pipe Specifications:

670’ of 60” OD x 1.625” wall T-7 Permalok®

160’ of 60” OD x .844” wall T-7 Permalok®

Tons:

388

Owner:

Old Dominion Electrical Cooperative

Engineer Firm:

Burns & McDonell

Contractor:

Bradshaw Construction

Virginia-based Old Dominion Electrical Cooperative provides power to 11 local cooperatives. The new natural gas-fired Wildcat Point Generation Facility in Cecil County, Maryland, supplies power to approximately 400,000 homes. Permalok casing pipe played a critical role in this project by being used for an intake shaft and conveyance pipeline installed via Microtunnelling that cycles water from the Susquehanna River.

Due to the nature of an intake and the overall soil conditions of very soft silts and clays, the design team chose the Permalok® T-7 joint. To combat the buoyant by nature of steel pipe, we teamed with Bradshaw Construction to develop a solution to provide sufficient weight to counteract the concerns of buoyancy. We upsized the casing and installed internal cast iron ingots to provide sufficient weight to counter act buoyancy. During manufacturing, we installed the ingots and encased them within a 5/8” steel plate. This created a usable cross section to allow for the installation of the various utilities to be installed within the intake.

Geotechnical conditions including transition from rock to very soft silty soils created a number of challenges in selecting both the correct equipment and the correct pipe. The soil conditions required constant tunnel operation to prevent the settling of the MTBM and subsequent flotation of the pipe. The use of ballast to counteract buoyant forces while still providing sufficient space for the structure to perform its intended task was a new development in the industry. Our collaborative effort between all parties resulted in the successful completion of a new methodology utilizing the proven performance of Permalok® pipe.